Drafting machine band tightening device



2 Sheets-Sheet 1 Filed Nov. 22, 1940 ATTO/Q/YEY.

y 1941- F. G. EUBANKS 2,243,732

DRAFTING MACHINE BAND TIGHTENING DEVICE Filed NOV. 22, 1940 2Sheets-Sheet 2 wwmmlmllllz/jliilliiyzlz Patented May 27, 1941 UNITEDSTATES PATENT OFFICE DRAFTING MACHINE BAND TIGHTENING DEVICE Floyd G.Eubanks, Pasadena, Calif., assignor of forty-seven and one-half per centto Francis E. Vaughan, Pasadena, Calif., and five per cent to Robert M.McManigal, Compton, Calif.

Application November 22, 1940, Serial No. 366,664

Claims.

ing head includes a protractor and a proti-actor -arm provided with aVernier or witness point and with means for holding one or more rulersor straight edges which can be rotated about the protractor. As thedrafting head is moved over the drawing board, orientation of theprotractor is held constant by a combination of pulleys and bands.

The object of my invention is to provide, in a drafting machine of theband and pulley type, a flexible construction which permits the scalesin the drafting head to lie flat upon the drafting board.

Another object of my invention is to provide, in a drafting machine ofthe band and pulley type, a flexible construction which permits thedrafting head to be moved freely with respect to the board withoutincreasing or decreasing the tension in the bands.

Another object of my invention is to provide, in a drafting machine ofthe band and pulley type, an arm for holding apart two of the heads ofthe drafting machine in order to maintain proper tension in the flexibleband, which arm can be rotated with respect to said heads withoutaffecting the length of said arm, but which, nevertheless, can belengthened and shortened, as desired, by rotating one part of said armwith respect to another part of said arm.

Another object of my invention is to provide, in a drafting machine ofthe band andpulley type, an arm rotatable with respect to the head ateither end, said arm comprising a tubular part and a part adjustablewith respect to said tubular part, whereby the length of said arm can bechanged as desired to adjust the tension in the band.

My invention has many other objects, advantages, and features, some ofwhich, with the foregoing, will be apparent from the followingdescription and accompanying drawings of the invention. It should beunderstood, however, that these particular embodiments of the inventionare chosen for the purpose of exemplification, and I do not limit myselfto the forms shown, since the invention, as set-forth in the claims, maybe embodied in a large plurality of forms.

Referring to the drawings:

Figure 1 is a plan view of the drafting machine of the pulley and bandtype embodying my invention.

Figure 2 is a sectional view taken along the line 2-2 in Figure 1 andshowing the details of a preferred form of the band-tightening device.

Figure 3 is a view taken on theline 3-3 of Figure 2.

Figure 4 is a sectiona1 view taken along the line 4-4 in Figure 1 andshowing a modified form of my invention.

Referring to said drawings, the numeral It indicates any conventionalclamp for holding the drafting machine to a drawing board [2. The clampll carries a pivot shaft rising perpendicularly to the board, to whichis rigidly aflixed a single groove pulley (not shown) which isengaged bya band l3. An arm I4 is pivoted to the shaft by a suspension head IS. insuch a manner that it can be rotated about said shaft. At the other endof the arm I is the upper eibow head l6 which articulates about axis Hwith the lower elbow head l8 which is connected to one end of the armIS. A two-groove pulley (not shown) is mounted on the axis ofarticulation at ll between the elbow heads l6 and IS. The band 13engages one groove of this pulley and the band 20 engages the othergroove. The other end of the arm; I9 is connected to a head M, whichcarries a grooved pulley (not shown), which is engaged by the band 20.The pulley carries the protractor 22. A shaft passing through the head2! and the pulley (not shown) carries at its upper end the handle 23 andat its lower 'end the base plate 24. Said base plate is provided withscale chucks 25 and 26 carrying the scales 21 and 28.

The heads is and I8 each have a socket 29 defined by a cylindrical wall30 and an end wall 3!. For the purpose of holding the heads l5 and I6apart in order to maintain proper tension in the flexible band l3, thearm I is made adjustable in length so that by increasing or decreasingthe length of said arm I! the distance between the heads l5 and IE willbe changed.

In the preferred form of my invention, I

make the arm l4 adjustable by constructing it ofwtwo parts, namely, anadjustable part 33 which is threadedly connected to a tubular part 34.By causing relative rotation between the adjustable part 33 and thetubular part 34 of the arm, the length of the arm is changed.

The adjustable part 33 is preferably adapted to lie within the socket 29in the head IS. A

portion of the tubular part 33 extends into the socket 23. Said portionis cylindrical and is adapted to make a sliding fit with the innersurface of the cylindrical walls 33 of said socket 23 in order that thearm i 3 and the head it will be maintained in proper alignment and inorder that the arm l3 will be rotatably supported in said socket.

As clearly shown in Figure 2, a substantial clearance is providedbetween the adjustable part 33 and the walls of said socket. In orderthat theadjustable part 33 may be prevented from rotating with thetubular part 33 when an adjustment of length of arm is to be made, aportion of the adjustable part 33 outside of the tubular part 33 isprovided with one on more recesses 33, as shown in Figure 3, and anopening 33 is provided in the wall of the socket of the head IS. A pin31, passed through the opening 33, engages one of the recesses 35. Thepin 31 may be provided with a knurled head. A hardened steel ball 33 maybe provided in a socket at the end 39 of the adjustable part 33 and bearagainst a hardened steel thrust disk 33 which contacts the end wall 3|of the socket 23 in the head It.

The operation of the device is as follows:

when the head It is about to be assembled with the arm 13, theadjustable part 33 is screwed into the tubular part 33 as far aspossible. The end of the tubular part 33 carrying the adjustable part 33is pushed into the socket 23 of the head l3 as 'far as possible; thatis, until the steel ball 33 bears against the thrust disk 30. The otherend of said arm I3 is rotatably connected to the head IS. The band I3 isnow placed over the pulleys carried in the heads I! and I at either endof the arm 13. The pin 31 is introduced into one of the recesses 35through the opening 36 in the wall of the socket 23 of the head 13. Thetubular part 33 is then rotated, the adjustable part 33 being preventedfrom rotating by the pin 31, the direction of this rotation being suchas to screw the tubular part 33 away from the adjustable. part 33. Thisaction thrusts the tubular part 33 outward from the head I6 and therebytends to tighten the band l3 by increasing the distance between thepulleys carried in the heads l and I6. When the band I3 is suflicientlytight, the pin 31 is withdrawn from the opening 36 so that theadjustable part 33 is free to rotate with the tubular part 33.

If new the tubular part 33 is rotated, the adjustable part 33 willrotate with it, since the friction between the tubular part 33 and theadjustable part 33 is greater than the friction between the steel ball33 and the thrust disk 33. It is clear that the head It can swivel onthe end of the arm I3, the ball 33 and the disk 33 being the thrustbearings, without changing the position of the tubular part 33 and theadjustable part 33 relative to each other, and therefore withoutloosening the band l3 engaging the pulleys at either end of the arm [3.

A similar means may be provided to tighten the band 20 around thepulleys carried by the heads i3 and 2|. In the drawings, however, I haveillustrated a modification of my invention, as shown in Figure 4. Thearm l9 comprises four parts. The tubular part 3| is firmly fixed intoone end of the grip 32. An adjustable part 33 is screwed into the otherend of the grip 32. The other end of the adjustable part 33 is receivedby the socket 23 of the head l3. Into this end of the adjustable piece33 is fitted a plug 33 to rotate therewith. The plug '33 is providedwith one or more recesses, two of said recesses being shown at 35. A pin33 is adapted to pass through a hole 31 in the head l3 and engage one'ofthe recesses 35. A hardened steel ball 33 rests in a socket in the endof the plug 33 and bears against a thrust disk 33 at the inner end ofthe socket. The operation of this modification will be apparent from theforegoing description of the operation of the preferred form and willtherefore not be repeated herein.

Although I prefer to position the adjustable parts of the arms insockets in the elbow heads 13 and I3, they may be positioned in socketsin the heads l5 and 2|.

From the foregoing description taken in connection with the accompanyingdrawings the uses, advantages, and operation of the bandtighteningdevice of my invention will be readily understood by those skilled inthe art to which the invention appertains. While I have described theprinciple of operation, together with the forms of my invention which Inow consider to be the best embodiments thereof, I desire to have itunderstood that the forms shown are merely illustrative and that theinvention is not to be limited to the details disclosed herein, but isto be accorded the full scope of the appended claims.

I claim:

1. In a drafting machine of the band and pulley type, an arm comprisinga tubular part and an adjustable part, a head at one end of said arm,said head having a socket which is adapted to receive the adjustable endof said arm, a second head carried at the other end of said arm, apulley rotatably mounted on the first-mentioned head, a second pulleyrotatably mounted on the second-mentioned head, a hexible band extendingaround said two pulleys, the adjustable part of said arm threadedlyengaging the end of said tubular part within the socket of thefirst-mentioned head, said adjustable part having a recess on itsperiphery outside of said tubular part, a thrust bearing between saidadjustable part and the socket containing it, and an opening through thewall of said socket which is adapted to admit a pin to said recess insaid adjustable part for preventing the rotation of said adjustable partof said.

arm with respect to said tubular part of said arm.

2. In a drafting machine of the band and pulley type, an arm comprisinga tubular member internally threaded at one end and an adjustable partexternally threaded at one end, and in threaded engagement with saidtubular member, said adjustable part having a recess on its periphery, ahead having a socket adapted to admit said adjustable part, there beinga substantial clearance between said adjustable part and the walls ofsaid socket, a thrust bearing acting between said adjustable part andthe end wall of said socket whereby said arm is adapted to be rotatedwithout affecting the length of said arm, and an opening in the wall ofsaid socket which is adapted to admit a pin to said recess in saidadjustable part whereby the length of said arm may be changed byrotating the adjustable part with respect to said internally threadedtubular member.

3. In a drafting machine of the band and pulley type, an arm comprisinga tubular member internally threaded at one end and an adjustable partexternally threaded at one end and her, said adjustable part having arecess on its periphery, a head having a socket adapted to admit saidadjustable part, a thrust bearing acting between said adjustable partand the end wall of said socket, and an opening in the wall of saidsocket which is adapted, to admit a pin to said recess in saidadjustable part.

4. In a drafting machine of the band and pulley type, an arm comprisingtwo elongated members threadedly engaged longitudinally, an end portionof one of said members extending longitudinally beyond the other of saidmembers, said extending end portion being provided with a recess on itsperiphery, a head having a socket which is adapted to admit saidrecessed portion of said elongated member, a thrust bearing actingbetween said elongated member and the end of said socket, and an openingthrough the wall of said socket, said opening being adapted to admit apin to said recess in said elongated member.

. 5. In a drafting machine. of the band and pulley type, the combination'of an arm com- 1 prising-a first elongated member and a secondelongated member, said elongated members being threadedly engagedlongitudinally and one end of said first elongated member being extendedlongitudinally beyond said second elongated member, a head having asocket adapted to admit an end portion of said first elongated member, athrust bearing acting between said first elongated memberand said head,whereby said arm can be rotated without affecting the length of saidarm, a recess on the periphery of the portion of said first elongatedmember in said socket, and an opening in the wall of said socketwhich isadapted to admit a pin to said recess in said first elongated memberwhereby the length of said arm can be changed by the rotation of saidsecond elongated member with respect to said first elongated member.

FLOYD G. EUBANKS.

